1. Field of the Invention
The present invention relates to an antenna device, and more particularly, to an antenna device capable of operating two radiators as one antenna by feeding signals having different phases to the two radiators, respectively.
2. Description of the Related Art
An antenna is a device that transmits or receives radio waves.
The antenna in the field of mobile communications is a passive device which is sensitive to the external environment. The antenna is applied to, e.g., a base station, a repeater or a wireless communication device to receive an electric wave from the outside or transmit an electrical signal generated from a communication device to the outside.
In many cases a built-in antenna of a mobile communication terminal is required to optimize characteristics such as standing-wave matching for each mobile communication terminal to which the antennal is applied. When a bandwidth of the antenna is narrow, many tests need to be conducted for optimization. However, when the bandwidth of the antenna is wide, fewer tests are conducted, accordingly shortening the time for development.
Most of related art antennas for broadcasting reception are external antennas. To optimally receive broadcasting signals, the external antennas must be adjusted to a length of λ/4 of a frequency band for broadcasting reception. However, a general user cannot normally be aware of an accurate length of the antenna, and therefore it is difficult to obtain an optimum gain in the frequency band that is to be used for broadcasting reception.
In the case of a related art chip antenna, a feed structure and a radiator for a specific frequency band are designed by forming a radiation pattern, which is connected to a feeding part and a ground part, on a dielectric block. When the chip antenna is set in a mobile communication terminal, a frequency characteristic of the chip antenna changes and hence tuning operation is inevitable. However, the tuning operation is accompanied by modifications in the radiation pattern or design of the dielectric block, which causes manufacturing loss.